<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <ul>
        <li>项目1</li>
        <li class="selected">项目2</li>
        <li>项目3</li>
        <li>项目4</li>
        <li>项目5</li>
        <li id="n6">项目6</li>
    </ul>
    <style>
        /*标签选择器*/
        ul{
            list-style-type: square;
        }
        li{
            color: rgb(70, 133, 210);
        }
        /*类选择器*/
        .selected{
            background-color: aquamarine;
        }
        /*ID选择器*/
        #n6{
            color: brown;
        }
        /*通配选择器*/
        *{
            margin: 0px;
            padding: 5px;
        }

    </style>
</body>
</html>